‘If our surveillance had been weakened by having to try and avoid other surveillance teams looking for us, if we had lost the subject, he may have gone and committed further murders because we were dealing with something else,’ he said.

Suffolk police asked Soca to provide surveillance officers to follow suspects in the then-unsolved murders of five women, prompting the News of the World, which was closed down last year at the height of the phone hacking affair, to hire its own surveillance team.

Advertisement

Advertisement

Mr Harrison said the information the tabloid used to learn of the police surveillance would have come from ‘someone close to the investigation’.

The Soca officers realised they were being followed in 2006 after spotting vehicles in prime surveillance spots.

‘We identified them because they were sat in the position that we would sit in if we were doing the same job,’ Mr Harrison continued.

‘We were told that they were probably ex-special forces soldiers who would have a good knowledge of surveillance techniques.’

Mr Harrison was highly critical of the defunct paper’s actions, saying: ‘Murder suspects before they are arrested, before they realise they are being investigated, may return to the scene of the crime.

‘They may try to dispose of evidence, they may try to move bodies, they may even try to commit further offences.

‘If they thought they were being followed, they might very well stop what they were doing or not do what they had planned to do.

‘If a surveillance team cannot see the sort of evidence we were after, if that’s not possible, then that weakens the prosecution case in the future.’

Also appearing before the Leveson Inquiry into press ethics and standards, Daily Express crime correspondent John Twomey, who is also chairman of the Crime Reporters’ Association, said the News of the World’s behaviour was ‘shocking’.

‘It’s just quite unbelievable, really, that a newspaper should go to those lengths,’ he said.

‘I think it would have taken most reporters – certainly most crime reporters – by surprise.’

Steve Wright, then aged 48, was sentenced to a whole life term for the murder of the five women in 2008.